Spinach And Cheese Strata

Why I Love This Recipe
We used to make this at the restaurant along with the blueberry stuffed french toast for Sunday brunch. These satisfied both the sweet and the savory
Ingredients You'll Need
1 (10 ounce) package frozen spinach, thawed
1 1/2 cups finely chopped onions (1 large)
3 tablespoons unsalted butter
1 teaspoon salt
1/2 teaspoon black pepper
1/4 teaspoon freshly grated nutmeg
8 cups French bread or Italian bread, in 1 inch cubes (1/2 lb)
6 ounces coarsely grated gruyere (2 cups)
2 ounces finely grated parmigiano-reggiano cheese (1 cup)
2 3/4 cups milk
9 large eggs
2 tablespoons Dijon mustard
Directions
Squeeze handfuls of spinach to remove as much liquid as possible, then finely chop.
Cook onion in butter in a large heavy skillet over moderate heat, stirring, until soft, 4 to 5 minutes.
Add 1/2 teaspoon salt, 1/4 teaspoon pepper, and nutmeg and cook, stirring, 1 minute.
Stir in spinach, then remove from heat.
Spread one third of bread cubes in a buttered 3-quart gratin dish or other shallow ceramic baking dish and top evenly with one third of spinach mixture.
Sprinkle with one third of each cheese.
Repeat layering twice (ending with cheeses).
Whisk together milk, eggs, mustard, and remaining 1/2 teaspoon salt and 1/4 teaspoon pepper in a large bowl and pour evenly over strata.
Chill strata, overnight, covered with plastic wrap, (at least 8 hours for bread to absorb custard).
Preheat oven to 350F.
Bake strata, uncovered, in middle of oven until puffed, golden brown, and cooked through, 45 to 55 minutes.
Let stand 5 minutes before serving.